Method and Apparatus for Testing Attachment Joints

ABSTRACT

Apparatus tests the performance of joints between an attachment and a beam having a pair of caps connected by a corrugated web. The apparatus includes first and second grips contoured to the shape of a portion of the corrugated web for gripping the web. A force applicator coupled with the attachment and the grips applies force to the beam through the joint.

TECHNICAL FIELD

This disclosure generally relates to test fixtures, and deals moreparticularly with a test fixture apparatus and related method fortesting the performance of a joint between an attachment and a beam.

BACKGROUND

It is sometimes necessary to test the performance of attachment joints.For example, in the aircraft industry, a variety of attachments such as,without limitation, stanchions, seats, partitions and other fixtures maybe attached to either the top or the bottom of beams that support cargoor cabin floors. These attachments may be connected to the floor beam byvarious types of attachment hardware, such as, without limitation, seattracks which are used to mount passenger seats on the floor beams. Thefloor beams may comprise a pair of caps connected by a web that may beeither substantially straight and flat along the length of the beam, orcontain non-flat and/or undulating sections. Beams having non-flatand/or undulating webs may also be known as corrugated beams, referringto the corrugated-like shape of the web.

In the past, in order to test hardware joints between an attachment anda corrugated metal floor beam, the floor beam and the attachment wereconnected through test fixtures to a load test machine which appliedforce to the floor beam that loaded the web in shear. The test fixtures,which were specially fabricated for each load test, were permanentlyattached to a cap and/or the corrugated metal web of the beam, thusrendering them unsuitable for reuse. The irregular shape of thecorrugated web made it necessary to weld flat plates to short sectionsof the web in order to connect the web to the load test machine.Following a load test, the plates were not easily removed for possiblereuse because they were welded to the web. Accordingly, a fresh set ofplates had to be fabricated and fitted for each new load test.

Accordingly, it would be desirable to provide a method and test fixturefor testing joints between attachments and beams which allow reuse oftest fixture in order to reduce test cycle time, labor and materials. Itwould also be desirable to provide a method and test fixture that allowsa moment to be applied about the attachment, as the floor beam is beingshear loaded during a load test.

SUMMARY

In accordance with the disclosed embodiments, a reusable test fixture isemployed to react an applied attachment load in shear through thecorrugated web of a short floor beam section in order to simulate thelocal internal loads of a full length floor beam. The applied loads maybe either axial tension loads or compression loads, with or without amoment applied to an attachment joint on the beam. The embodimentsproduce internal floor beam loads that closely simulate floor beaminternal loads at the seat track or stanchion of an actual floor beaminstalled in an aircraft. Additionally, the reusable test fixture may bequickly attached to the floor beam in order to reduce test cycle time.

The test fixture is useful in rapidly generating design capabilitycurves for multi-axis applied loads and varying corrugated floor beamgeometries. The availability of these design capability curves maystreamline the stress analysis process and may reduce the design/buildcycle times for corrugated beams.

According to one embodiment, apparatus is provided for testing theperformance of a joint between a floor beam and an attachment to thefloor beam, wherein the floor beam includes a pair of caps connected bya corrugated web. The apparatus comprises first and second grips forgripping the ends of the web, and, means coupled with the attachment andthe grips for applying a force through the beam. Each of the gripsincludes first and second portions having faces contoured to generallymatch the contour of the corrugated web, and at least one fastener forreleasably clamping the web between the first and second grip portions.

According to another disclosed embodiment, apparatus is provided fortesting the performance of a joint between a seat track and a floor beamhaving a corrugated web, using a short section of the floor beam as atest specimen. The apparatus comprises means for holding the oppositeends of the web of the test specimen; a load applicator for applying aload on the test specimen through the centroid of the seat track; and, aconnection between the load applicator and the seat track formaintaining the direction of the applied load through the centroid ofthe seat track as the seat track deflects in response to the appliedload.

In accordance with a further embodiment, a reusable fixture is providedfor testing a short test section of a floor beam in order to simulatelocal internal loads on a full length beam, wherein the floor beamincludes a corrugated web connected between first and second caps. Thefixture comprises a load applicator for applying a load to the floorbeam in a direction that loads the corrugated web in shear; a set offirst reusable connections for releasably connecting the load applicatorto opposite ends of the corrugated web; an attachment mounted on one ofthe caps; and, a second reusable connection releasably connecting theload applicator with the attachment and reacting the applied loadthrough the attachment.

According to a disclosed method embodiment, testing the performance of ajoint between an attachment and a floor beam having a pair of capsconnected by a corrugated web, comprises: clamping each end of thecorrugated web; and, applying a shear load to the corrugated web throughthe attachment. The method may further include applying a moment aboutthe joint as the shear load is being applied to the web.

The disclosed embodiments satisfy the need for a method and apparatusfor testing joints between attachments and beams having corrugated webswhich overcome disadvantages of the prior test fixtures.

Other features, benefits and advantages of the disclosed embodimentswill become apparent from the following description of embodiments, whenviewed in accordance with the attached drawings and appended claims

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1 is a functional block diagram of apparatus for testing jointsbetween an attachment and a beam.

FIG. 2 is a side view of one embodiment of the apparatus.

FIG. 3 is a sectional view taken along the line 3-3 in FIG. 2.

FIG. 4 is a perspective view of an alternate embodiment of theapparatus.

FIG. 5 is an enlarged, sectional view taken in the area designated as“A” in FIG. 4.

FIG. 6 is an enlarged sectional view of the area designated as “B” inFIG. 5.

FIGS. 7 and 8 are side views illustrating the application of a moment tothe floor beam shown in FIG. 4.

FIG. 9 is a diagram illustrating a technique for measuring thedeflection of a seat track during a load test.

FIG. 10 is a flow diagram of a method of testing the performance of ajoint between an attachment and a floor beam.

FIG. 11 is a flow diagram of aircraft production and servicemethodology.

FIG. 12 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring first to FIG. 1, a reusable test fixture 10 includes a loadapplicator 11 for applying shear loads and/or bending moments through ajoint 13 between an attachment 15 to a floor beam 14. The floor beam 14is held by a pair of grips 24, and the load may be applied through apivotal connection 17 between the load applicator and the attachment 15.As will be discussed in more detail below, the attachment 15 maycomprise any of a variety of structural members, fixtures or hardware,and the floor beam 14 may comprise only a short section of a full lengthfloor beam that is used as a test specimen to determine the performanceof the joint 13 between the floor beam 14 and the attachment 15.

Referring now to FIGS. 2 and 3, in one embodiment, a test fixture 10 abroadly includes a load applicator 11 and a pair of grips 24 a fortesting a joint 13 between an attachment 15 in the form of a seat track12 and a floor beam 14. Although a seat track 12 is illustrated in FIG.2, it is to be understood that any of various other forms ofattachments, hardware, fixtures or structural members may comprise anattachment 15 to the floor beam 14. The seat track 12 includes generallyflat, spaced apart flanges 12 a, 12 b, and a central, longitudinallyextending opening 22 having a generally rectangular cross section.

The floor beam 14 comprises a pair of caps 18, 20 connected by acorrugated web 16 whose length extends from right to left as viewed inFIG. 2. The corrugated web 16 may possess any of various geometricconfigurations, such as, for example and without limitation, a sinewave, a square wave or a saw tooth wave. The floor beam 14 may be formedof metal, composite materials or combination of metal and compositematerials. For example, the caps 18, 20 may be formed of a carbon fiberreinforced polymer resin and the web 16 may be formed of a metal suchas, without limitation, titanium. The caps and the web 16 may be formedof other composite materials such as, without limitation, metallic orceramic composites. In accordance with the disclosed embodiments, thefloor beam 14 comprises a section representing a test specimen of alonger floor beam (not Shown) that may be installed in an aircraft (notshown).

The seat track 12 is fastened to the upper cap 18 by means of fasteners21 that pass through the lower flange 12 a, the upper cap 18 and radiusfillers 19 that are formed on the bottom of the cap 18. Nuts 23 andwashers (not shown) may be used to secure the ends of the fasteners 21on the cap 18. The grips 24 include first and second portions 24 a, 24b, each of which includes a contoured surface 31, 33 matching that ofthe web 16. The outer ends of the web 16 are clamped between the firstand second portions 24 a, 24 b of the grips 24 by means of a fastener 28that passes through a hole 35 formed in the web 16 and an opening 29 inthe grip 24 which is aligned substantially normal to a generally flatsection 34 of the web 16. The first and second portions 24 a, 24 b ofthe grips 24 may include countersunk holes 26 for respectively receivingthe ends 30, 32 of the fastener 28. Clamping of the grips 24 to theextremities 27 of the web 16 is used to transfer the loads between theload applicator 11 and the test specimen.

The lower end of each of the grips 24 includes a recess 36 partiallyformed by retainer plates 38 that may be removably held on the bottom ofthe grips 24 by fasteners 37. The outer ends of the lower cap 20 arecaptured within the recess 36.

The load applicator 11 may take various forms, depending upon theparticular application and load testing machine (not shown) that is usedto generate the load forces. In the illustrated example, the loadapplicator 11 includes a U-shaped clevis 42 that is connected by a pivotpin 48 through a force applying member 46 that may apply an axial forcein either direction indicated by the arrow 50. The clevis 42 may be issecured to the seat track 12 by means of a fastener 44. The pivotalconnection formed between the clevis 42 and the pivot pin 48 allows aslight relative rotational moment between the force applying member 46and the seat track 15, about the axis of pivot pin 48, therebymaintaining application of the load in the direction 50. The loadapplicator 11 may further include a member such as a flat plate 49 thatis secured to the bottom of the grips 24 by means of the retainer plates38 and fasteners 40. Member 49 may be stationarily mounted on a base(not shown) and thus acts as a stationary member against which theapplied forces may react, or may form part of the load test machine (notshown) that applies axial force in either direction 50.

In use, a test specimen may be provided by cutting a short section of afloor beam 14 from a longer full length floor beam (not shown). The seattrack 12 may then be secured to the upper cap 18 by means of suitablefasteners 21. Next, the grips 24 may be installed by positioning thefirst and second portions 24 a, 24 b on opposite sides of the web 16,near the outer extremities 27 of the floor beam 14. A hole 35 is formedin the web 16 that is aligned with the through hole opening 29 in eachof the grips 24. Fasteners 28 may then be installed and tightened,thereby clamping the first and second portions 24 a, 24 b of the grips24 on the ends of the web 16. The retainers 38 may be fastened to thebottom of the grips 24, thereby clamping the lower cap 20 on the grips24. The clevis 42 is fastened to the seat track 12 using the fastener44. The load applying member 49 may be fastened to the retainers 38 orother portions of the grips 24 using fasteners 40.

With the assembled seat track 12 and beam 14 installed in the testfixture 10 a as described above, a shear load may be imposed on the web16 through the seat track 12 by axially displacing the load applicator11 to produce either tension or compression, as desired, in the testspecimen. The load test may be either a static test that tests staticproperties of the test specimen, or it may be a dynamic test in which aseries of either the same or different loads are applied to the testspecimen. The load test may reveal information concerning the static ordynamic performance of the attachment joint 13, the attachment 15itself, the floor beam 14, or the combination of these structuralelements. Following completion of one or more the load tests, the testfixture 10 a may be disassembled by simply removing the grips 24 andreleasing fasteners 37, 40 and 44 which allow removal of the testspecimen, thus readying the test fixture 10 a for reuse with anothertest specimen.

Attention is now directed to FIGS. 4-6 which depict an alternateembodiment of the test fixture 10 b. Test fixture 10 b is similar to thetest fixture 10 a previously described, but further includes asemi-spherical, pivotal connection 13 between a load applicator fitting56 and the seat track 12. The seat track 12 includes a plurality oflongitudinally spaced, aligned through holes 54 in the top flange 12 bthat represent alternate choices for fastening a seat (not shown) to theseat track 12. When the load applicator fitting 56 is connected to theseat track 12 using one of the through holes 54 that is offset oreccentric by a distance “E” relative to the web 16, a force applied tothe seat track 21 by the load applicator 11 through the fitting 56results in both a shear load being applied to the web 16, as well as abending moment applied being to both the seat track 12 and the flange18, which in turn transfer the moment to the upper cap 18.

As best seen in FIGS. 5 and 6, a solid insert 58 is disposed within thelongitudinal opening 22 in the seat track 12. The semi-spherical pivotalconnection 13 comprises a semi-spherical lobe 64 on the end of a lug 62forming an extension of the load applicator fitting 56. The lug 62passes through a through hole 54 and a cylindrical passageway 60 formedin the insert 58. The insert 58 includes a semi-spherical cavity 66 thatconformally engages the lobe 64, allowing the central axis 57 of theload applicator 56 to pivot and/or rotate in any direction by an angle θuntil the lug 62 bottoms out on the insert 58. The size and position ofthe cavity 66 is chosen such that the bottom of the lobe 64 ispositioned at the centroid “C” of the seat track 12. The bottom of thelug 64 remains centered at the centroid “C” regardless of therotational/pivotal position of the load applicator fitting 56.

Referring now to FIG. 7, when the load applicator fitting 56 shown inFIGS. 4-6 is connected to the seat track 12 at a through hole 54 a thatis axially aligned with the web 16, a pulling force “P” may act in thedirection of the arrow 67 along an axis 69 passing vertically throughthe web 16. However, as shown in FIG. 8, when the load applicatorfitting 56, including the pivotal connection 17, is fastened to the seattrack 12 at a through hole 54 b offset from the axis 69 of web 16, thepulling force P acts along an axis 71 spaced from the web 69 by adistance “E”, thereby resulting in a bending moment being applied alongthe length of the seat track 12 that is substantially equal to P×E. As aresult of the bending moment applied to the seat track 12, both the seattrack 12 and the upper cap 18 may deflect. During this deflection, theload applicator fitting 56 is allowed to rotate/pivot relative to theseat track 12 so that the axis 57 (see FIG. 6) of the force appliedthrough the load applicator fitting 56 remains aligned with, and passesthrough the centroid C.

FIG. 9 illustrates a technique for measuring the amount of deflectionproduced by the bending moment applied to the seat track 12. A laser 68or similar beam generating device, may be mounted either on the upperflange 12 b of the seat track 12, or on the upper cap 18 of the beam 14.The laser 68 directs a beam 75 onto a surface 70. In response to thebending moment applied by the load applicator fitting 56, the seat trackflange 12 b (as well as the upper cap 18) may deflect by a distance d₁,causing the laser 68 to be displaced. This displacement of the laser 68causes the laser beam 75 to be deflected by a distance d₂ on surface 70,proportional to, but greater than the deflection to d₁.

Attention is now directed to FIG. 10 which illustrates the steps of amethod of testing the strength of the joint 13 between the attachment 15and the floor beam 14 (FIG. 1). A test specimen is prepared at 80 byforming a section of floor beam 14 as shown at 82, and installing theattachment 15 on the floor beam 14, as indicated at step 84. Next, at86, the web 16 is clamped by installing the grips 24 on the outerextremities 27 of the web 16. An optional pivotal connection 17 may beformed between the attachment 15 and the load applicator 11, as shown atstep 88. At step 90, the load applicator 11 may be connected to thefloor beam 14 and to the attachment 15. Then, at step 92, a shear loadmay be applied to the web 16 through, without limitation, the centroidof the attachment 15. Simultaneously with step 92, a moment may beapplied about the attachment 15, as shown at optional step 94. Thepivotal connection 17 is used to maintain the direction of the appliedload, as indicated at 96.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine and automotive applications. Thus, referringnow to FIGS. 11 and 12, embodiments of the disclosure may be used in thecontext of an aircraft manufacturing and service method 100 as shown inFIG. 11 and an aircraft 102 as shown in FIG. 12. During pre-production,exemplary method 100 may include specification and design 104 of theaircraft 102 and material procurement 106. During production, componentand subassembly manufacturing 108 and system integration 110 of theaircraft 102 takes place. Thereafter, the aircraft 102 may go throughcertification and delivery 112 in order to be placed in service 114.While in service by a customer, the aircraft 102 is scheduled forroutine maintenance and service 96 (which may also include modification,reconfiguration, refurbishment, and so on).

Each of the processes of method 100 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 12, the aircraft 102 produced by exemplary method 100may include an airframe 118 with a plurality of systems 120 and aninterior 122. Examples of high-level systems 120 include one or more ofa propulsion system 124, an electrical system 126, a hydraulic system128, and an environmental system 130. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 100. Forexample, components or subassemblies corresponding to production process108 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 102 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 108 and 110, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 102. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft82 is in service, for example and without limitation, to maintenance andservice 116.

Although the embodiments of this disclosure have been described withrespect to certain exemplary embodiments, it is to be understood thatthe specific embodiments are for purposes of illustration and notlimitation, as other variations will occur to those of skill in the art.

1-8. (canceled)
 9. An Apparatus for testing the performance of a jointbetween a seat track and a beam having a corrugated web, using a shortsection of the beam as a test specimen, comprising: means for holdingopposite ends of the corrugated web of the test specimen; a loadapplicator for applying a load to the test specimen through a centroidof the seat track; and a connection between the load applicator and theseat track for maintaining a direction of the applied load through thecentroid of the seat track as the seat track deflects in response to theapplied load.
 10. The apparatus of claim 9, wherein the connectionincludes: an insert adapted to be inserted into the seat track andincluding a cavity having a semi-spherical surface, and a generallysemi-spherically shaped lobe rotatable within the cavity andcomplementally engaging the semispherical surface of the cavity.
 11. Theapparatus of claim 10, wherein the connection includes: a lug extendinginto the seat track and connecting the lobe with the load applicator.12. The apparatus of claim 9, wherein the connection is laterally spacedfrom the corrugated web, resulting in a moment being applied to thejoint by the load applicator.
 13. The apparatus of claim 9, wherein themeans for holding opposite ends of the corrugated web includes: firstand second grips respectively on the opposite ends of the corrugatedweb, and means for removably mounting the first and second grips of theweb.
 14. The apparatus of claim 13, wherein each of the first and secondgrips includes at least one face engaging, and having a contourgenerally matching the contour of, the corrugated web.
 15. A reusablefixture for testing a short test section of a beam in order to simulatelocal internal loads on a full length beam, wherein the beam includes acorrugated web connected between first and second caps, comprising: aload applicator for applying a load to the beam in a direction thatloads the corrugated web in shear; a set of first reusable connectionsfor releasably connecting the load applicator to opposite ends of thecorrugated web; an attachment mounted on one of the caps; and a secondreusable connection releasably connecting the load applicator with theattachment and reacting to the applied load through the attachment. 16.The reusable fixture of claim 15, wherein: the set of first reusableconnections includes first and second grips, each of the first andsecond grips including first and second portions and fasteners forclamping an end of the corrugated web between the first and secondportions of the grip.
 17. The reusable fixture of claim 15, wherein thesecond reusable connection includes a semi-spherical connection betweenthe load applicator and the attachment and allowing the attachment torotate relative to the load applicator. 18-23. (canceled)
 24. A methodof testing the strength of a joint between an attachment such as a seattrack or a stanchion and a beam having a pair of caps connected by acorrugated web, comprising: providing a short section of the beam;fixing the attachment to one of the caps of the short beam section;releasably clamping ends of the corrugated web of the short beamsection; forming a semi-spherical connection between a load applicatorand the attachment; using the load applicator to apply a shear load tothe corrugated web through the attachment while applying a moment aboutthe attachment; and, allowing the attachment to rotate relative to theload applicator through the semi-spherical connection while the momentis being applied about the attachment.
 25. An Apparatus for testing thestrength of a joint between an attachment such as a seat track or astanchion and a beam having a pair of caps connected by a corrugatedweb, comprising: a pair of releasable grips for gripping opposite endsof a short test section of the beam, each of the grips including firstand second portions between which the web may be clamped, each of thefirst and second portions including opposing faces contoured togenerally match the contour of the corrugated web, each of the gripsfurther including a recess for receiving the ends of one of the caps;retainers for retaining the ends of the one cap within the recess ineach of the grips; a load applicator for applying a shear load to thecorrugated web through the attachment; and a generally semi-sphericalconnection between the load applicator and the attachment formaintaining the direction of the applied load through a centroid of theattachment as the attachment deflects in response the applied load.